Power conversion devices, typified by inverters, use pulse width modulation (PWM) to achieve a DC to AC conversion or AC to DC conversion function. Inverters are used in, for example, driving systems for synchronous motors, induction motors, and other AC motors (referred to below as motors).
A power conversion device for driving a motor needs a means for detecting phase current to achieve precise control. Recently, methods of obtaining information about AC current flowing in a motor from DC bus current in a power conversion device, without having to use an external current detecting means such as a current sensor, are proposed in, for example, Patent Document 1, Patent Document 2, and Patent Document 3. These technologies eliminate the need to use a specific current sensor, so the number of parts in a device and thereby reduction in space and manufacturing costs becomes possible.